Copending application Ser. Nos. 503,146, 503,201, and 503,212, filed Sept. 4, 1974, now abandoned and incorporated into Continuation-in-Part application Ser. Nos. 574,662, 574,829, and 574,664, respectively, filed May 5, 1975, which are assigned to the same assignee as the present application, disclose new and improved elevator systems in which the strategy utilized by the supervisory control is suitable for a microprocessor, such as Intel's MCS-4 and MCS-8, Rockwell's PPS, Signetics's PIP, National's GPC/P and AMI's 7300. These applications will be hereinafter referred to as the earlier filed copending applications. The microprocessor offers an attractive cost package as well as flexibility due to the LSI circuitry and programmability. When the microprocessor offers programming flexibility at a modest cost, it imposes certain restrictions due to its relatively limited speed and memory capacity. The earlier filed copending applications set forth a universal operating strategy which accommodates all possible building configurations in which an elevator car may serve any combination of floors. The car controllers provide complete information to the system processor as to the building configuration which exists at any instant, and thus the supervisory control may be universally applied to any building without any significant modification.
The strategy operates within the limited operating speed of a microprocessor, because it does not decide when a hall call is registered which car should serve the call and then output the assignment of the call in a timely manner to a car. Rather, it periodically assigns the up and down service directions of the floors to the cars by dividing them among all in service elevator cars within the constrains of predetermined dynamic averages, which distributes the work load evenly among all of the elevator cars. Thus, the car assigned to a specific service direction from a floor will immediately see a hall call registered therefrom without any intercession required on the part of the supervisory control system.
Before each new assignment process, the supervisory system control clears all previously assigned landing service directions which do not have a registered hall call associated therewith. Assigned landing service directions which have a registered hall call associated therewith are not cleared and reassigned, as it could result in unnecessary movement of cars which start out to answer a hall call registered from an assigned landing service direction and suddenly no longer see the hall call when the assignment of the associated landing service direction is cleared and then reassigned, possibly to another elevator car.